Engine Torque Calculator
Find the torque an engine produces at a given RPM from its horsepower.
How to use the Engine Torque Calculator
- Enter the horsepower and pick its unit.
- Enter the engine speed.
- Press Calculate. The result updates automatically as you type, and you can switch the result unit at any time.
About the Engine Torque Calculator
Horsepower and torque are not independent numbers: horsepower is torque multiplied by engine speed. If you know one at a given RPM, you can always find the other. That is useful for reading dyno sheets, checking a manufacturer's claims, or estimating how much twisting force reaches the transmission at the RPM where peak power occurs.
Note that peak horsepower and peak torque usually occur at different engine speeds. Entering an engine's peak horsepower and its peak-power RPM gives the torque at that RPM, which is normally lower than the advertised peak torque. On any dyno chart that plots both in lb-ft and hp, the curves cross at exactly 5,252 rpm.
Formula
Torque (lb-ft) = Horsepower × 5,252 ÷ RPM
Torque (N·m) = Power (kW) × 9,549 ÷ RPM
The 5,252 constant comes from 33,000 ft·lb/min per horsepower divided by 2π. Example: 300 hp at 4,500 rpm = 300 × 5,252 ÷ 4,500 ≈ 350.1 lb-ft.
Example calculation
Using the default values:
- Horsepower = 300 hp
- Engine speed = 4500 rpm
the calculator returns:
- Torque: 350.14 lb·ft
- Torque (metric): 474.73 N·m
Frequently asked questions
Why do horsepower and torque cross at 5,252 rpm?
Because hp = torque × rpm ÷ 5,252. When rpm equals 5,252, the two numbers are the same, as long as they are plotted in hp and lb-ft.
Is more torque better than more horsepower?
Torque at low RPM makes a vehicle feel strong pulling away and towing; horsepower determines acceleration and top speed at higher speeds. Gearing converts between the two.
How do I convert lb-ft to N·m?
Multiply by 1.3558. 350 lb-ft ≈ 474.6 N·m.
Last updated: · Category: Automotive calculators